Note: Descriptions are shown in the official language in which they were submitted.
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CEMENTITIOUS COMPOSITES VIA CARBON-BASED NANOMATERIALS
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority to
U.S. provisional application
62/914,867 filed October 14, 2019 the contents of which are incorporated
herein by
reference.
FIELD OF THE INVENTION
[0002] The present application relates generally
to composites and methods of
making cementitious composites with improved properties such as, for example,
higher
compressive strength, tensile strength, Young's modulus, durability, thermal
and/or
electrical conductivity, a lower shrinkage and/or a modified viscosity using
various forms
of additive carbon including graphene and coal-based materials.
BACKGROUND AND SUMMARY
[0003] Concrete and cement are one of the most
used materials in the world for
construction of, for example, buildings, roads, and the like. What is needed
is binder
formulations and methods of making them wherein the cemenfitious composite has
improved properties.
[0004] Advantageously, the instant application
provides composites with improved
properties such as increased compressive and tensile strengths that can be
made
efficiently and effectively with only small amounts of additives. Accordingly,
such
composites may be made cost-effectively using carbon-based nanomaterials made
from
a wide variety of carbon starting materials including waste products such as
plastic.
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[0005] In one embodiment, the present application
pertains to a cementitious
composite comprising graphene with at least 0.01% by weight of cement.
Advantageously, the composite may be characterized by (a) a compressive
strength of at
least about 15% greater than a compressive strength of the composite in
absence of
graphene; or (b) a tensile strength of at least about 15% greater than a
tensile strength of
the composite in the absence of graphene; or (c) both (a) and (b).
[0006] In one embodiment, the present application
pertains to concrete which
comprises at least cement, sand, and gravel and water and where at least 0.01%
by weight
of the its cement is graphene. Advantageously, the composite may be
characterized by
(a) a compressive strength of at least about 15% greater than a compressive
strength of
the concrete in absence of graphene; or (b) a tensile strength of at least
about 15% greater
than a tensile strength of the concrete in the absence of graphene; or (c)
both (a) and (b).
[0007] In another embodiment, the present
application pertains to a method for
making a composite having increased performance comprising first (a)
dispersing carbon
based material in water and (b) mixing this treated water with cement or
cement, sand
and gravel. The mixture is then cured to form a high performance composite.
[0008] In another embodiment, the present
application pertains to a method for
making a composite having increased strength comprising first (a) dispersing
carbon
based material in water using less than 2% surfactant and (b) mixing this
treated water
with cement or cement, sand and gravel. The mixture is then cured to form a
high
strength composite.
[0009] In another embodiment, the present
application pertains to a method for
making a composite having increased performance comprising dispersing carbon
based
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material as an additive in a wet (not cured) cement. The mixture is then mixed
and cured
to form a high performance composite.
[0010] In another embodiment, the present
application pertains to a method for
making a concrete having increased performance comprising dispersing carbon
based
material as an additive in a wet (not cured) concrete mortar. The mixture is
then mixed
and cured to form a high performance concrete.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] A more complete appreciation of the present
invention, and many of the
attendant advantages thereof, will be readily apparent as the present
invention becomes
better understood by reference to the following detailed description when
considered in
conjunction with the accompanying drawings, in which like reference symbols
indicate
the same or similar components, wherein:
[0012] Figure 1 shows 7-day compressive strength of 2" Portland cement cubes
(type
VID reinforced by turbostratic graphene (or flash graphene).
[0013] Figure 2 shows 28-day compressive strength of 2" Portland cement cubes
(type
I/II) reinforced by turbostratic graphene.
[0014] Figure 3 shows 7-day compressive strength of 2" Portland cement cubes
(type
VII) reinforced by turbostratic graphene made from HDPE.
[0015] Figure 4 shows 7-day compressive strength of 2" Portland cement cubes
(type
VII) reinforced by turbostratic graphene made from various feedstocks.
[0016] Figure 5 shows 28-day compressive strength of 4"x8" concrete cylinders
with
two different types of graphene.
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[0017] Figure 6 shows representative 7 day results, demonstrating increase in
compressive strength of 1" cube OPC composites, fly ash composites, and slag
composites
comprised of various wt% of graphene I (turbostratic graphene obtained from
carbon
black derived from pyrolyzed rubber tires).
[0018] Figure 7 shows representative 7 day results, demonstrating increase in
compressive strength of 1" cube OPC composites, fly ash composites, and slag
composites
comprised of various wt% of graphene II (turbostratic graphene obtained from
waste
plastics derived pyrolysis ash).
[0019] Figure 8 shows representative 7 day results, demonstrating increase in
compressive strength of 1" cube OPC composites, fly ash composites, and slag
composites
comprised of various wt% of graphene III (turbostratic graphene obtained from
shredded
raw rubber tires with 5% carbon black as conductive filler).
[0020] Figure 9 shows representative 28 day results, demonstrating increase in
compressive strength of 4"x8" concrete cylinders with OPC, flyash, or slag
binders
comprised of optimal wt% of graphene I (turbostratic graphene obtained from
carbon
black derived from pyrolyzed rubber fires).
[0021] Figure 10 shows representative 28 day results, demonstrating increase
in
compressive strength of 4"x8" concrete cylinders with OPC, flyash, or slag
binders
comprised of optimal wt% of graphene II (turbostratic graphene obtained from
waste
plastics derived pyrolysis ash).
[0022] Figure 11 shows representative 28 day results, demonstrating increase
in
compressive strength of 4"x8" concrete cylinders with OPC, flyash, or slag
binders
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comprised of optimal wt% of graphene III (turbostratic graphene obtained from
shredded
raw rubber tires with 5% carbon black as conductive filler).
[0023] Figure 12 shows representative 28 day results, demonstrating >20%
increase in
compressive strength of concrete samples with respect to the control concrete
sample.
[0024] Figure 13 shows direct conversion of carbon feedstock (e.g. coal) to
water
soluble graphene/graphitic structures for reinforcing cementitious composites.
[0025] Figure 14(a)-(b) show representative results for 7-day compressive
strength of
2"cement cubes reinforced by mainly bituminous coal, b-coal in Figure 14(a)
and calcined
pet coke in Figure 14(b).
[0026] Figures 14(c)-(d) show compressive strength of various concrete
cylinders at 7
days in Figure 14(c) and at 28 days in Figure 14(d).
DETAILED DESCRIPTION OF THE INVENTION
[0027] The general inventive concept is described
more fully below with reference
to the accompanying drawings, in which exemplary embodiments of the present
invention
are shown. As those skilled in the art would realize, the described
embodiments may be
modified in various different ways, all without departing from the spirit or
scope of the
present invention. The present invention should not be construed as being
limited to the
embodiments. Accordingly, the drawings and description are to be regarded as
illustrative
in nature to explain aspects of the present invention and not restrictive.
Like reference
numerals in the drawings designate like elements throughout the specification,
and thus
their description have not been repeated.
Increased Strength Composite and General Method
[0028] In one embodiment, the application pertains
to a composite comprising
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cement and carbon-based material. The type of cement used in the composites of
the
application is not particularly critical so long as its properties such as
compressive
strength and/or tensile strength are capable of being increased with the
addition of carbon-
based material as taught herein. The type of cement employed may vary
depending
upon the specific use of the cement (such as cement Type I, II, III, IV, V.
calcium
aluminate-based cement, calcium sulfate-based cement, calcium sulfoaluminate-
based
cement, pozzolan-based cement, limestone calcined clay cement, class H and (3
cements,
white cement, activated wastes as cement such as alkali activated flyash C,
Flyash F,
bottom ash, boiler slag, granulated blast furnace slag, bauxite residues, coal
combustion
residues, thenno activated clay, or any combination of these), the amount and
type of
carbon-based material to be added, the desired properties, and the method of
making the
composite.
[0029] In one embodiment, the application pertains
to a composite comprising
concrete and carbon-based material. The type of concrete used in the
composites of the
application is not particularly critical so long as its properties such as
compressive
strength and/or tensile strength are capable of being increased with the
addition of carbon-
based material as taught herein. The type of concrete employed may vary
depending
upon the specific use of the concrete, the amount and type of carbon-based
material to be
added, the desired properties, and the method of making the composite.
[0030] As used herein "binder" or "cement"
includes typical cementitious materials
made from cement Type I, II, III, IV, V, calcium aluminate-based cement,
calcium
sulfate-based cement, calcium sulfoaluminate-based cement, pozzolan-based
cement,
limestone calcined clay cement, class H and G cements, white cement, activated
wastes
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as cement such as alkali activated flyash C, Flyash F, bottom ash, boiler
slag, granulated
blast furnace slag, bauxite residue, coal combustion residues, thenno
activated clays, or
any combination of these.
[0031] As used herein concrete includes typical
concrete materials made from
above-described binder or cement with aggregate and water based mixtures, as
well as
concrete with additives such as fumed silica, air entrainers, plasticizers,
retarders, and the
like.
[0032] The carbon based nanomaterials may also be
referred to herein as "graphene"
and may be from virtually any carbon source. Such carbon based nanomaterials
or
graphenes used may include, for example, traditional graphene and its
variations as
described herein, as well as graphene that takes the form of quantum dot
particles instead
of large sheets. In some instances, the carbon based nanomaterials may include
an
oxidized form of a carbon based nanomaterial described herein. Some examples
include
an oxidized form of coal, coke, shungite, asphaltenes, acetylene black,
petroleum coke.
In some cases, the graphene may comprises less than 10 layers or comprises
more than
layers and may comprise graphite. In some embodiments the composite of claim
1,
wherein the graphene comprises turbostratic graphene or flash graphene as
described in
W02020051000 (Application PCTIU52019/04796) which is incorporated herein by
reference. In some embodiments the graphene comprises bemal stacked graphene
or
nanoplatelets, or tubostratic graphene or the combination thereof In some
embodiments,
tiu-bostratic graphene is at least 90 wt% of the bulk graphene material
produced.
[0033] The graphene may be derived from any
suitable source. Such sources
include, for example, feces, plastics, vinyl polymers, condensation polymers,
step-growth
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polymers, chain-growth polymers, living polymers, rubbers, humic acid,
carbohydrates,
rice powder, food waste, food, coal, organic waste, organic material,
bituminous coal,
coke, shungite, asphaltenes, acetylene black, carbon black, petroleum coke,
oil, petroleum
products, carbon from the stripping of the non-carbon atoms off of natural gas
or oil or
carbon dioxide, wood, cellulose, leaves, branches, grass, biomass, animal
carcasses, fish
carcasses, proteins, and mixtures thereof The type of coal is not particularly
limited
and includes, for example, a coal selected from anthracite, bituminous, sub-
bituminous,
lignite, or a mixture thereof Similarly, the type of plastic is not limited
and includes,
for example, a plastic selected from high-density polyethylene (HDPE), low-
density
polyethylene (LDPE), polyvinyl chloride (PVC), polypropylene (PP),
polyactylonitrile
(PAN), Polyethylene terephthalate (PET), or a mixture thereof
[0034] In some embodiments, there are heteroatorns
present in the feedstock to
afford a doped or heteroatom-containing graphene product. In some embodiment,
the
heteroatoms are selected from a group consisting of nitrogen, phosphorous,
phosphines,
phosphates, boron, metals, setnimetals, melamine, aminoborane, melamine-
formaldehyde resin, and mixtures thereof.
[0035] In some embodiments, there are chemical
covalent functionalization of
turbostratic graphene, wherein the functionalization atom is selected from a
group
consisting of oxygen, carbon, metals, sulfur, phosphorous, non-metals,
metalloids, and
combinations thereof
[0036] In some embodiments, there are chemical non-
covalent functionalization of
turbostratic graphene by one or more of surfactants, proteins, polymers,
aromatics, small
organic molecules, gases, groundwater contaminants, biological cells,
microorganisms,
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polychlorinated biphenyls, perchlorates, and borates.
[0037] In some embodiments, the (a) turbostratic
graphene comprises a plurality of
graphene sheets, and (b) the graphene sheets comprise predominately sp2-
hybridized
carbon atoms.
[0038] In some embodiments, the graphene sheets
comprise at least 70 atom% 5p2-
hybridized carbon atoms_
[0039] In some embodiments the graphene is a
mixture of two or more of any of the
types of graphene described herein.
[0040] Generally, the graphene comprises an amount
of a composition (such as a
sheared graphene dispersion in water) that is sufficient such that a composite
made
therefrom may be characterized by an improvement in one or more properties
such as (a)
a compressive strength of at least about 15%, or at least about 20%, or at
least about 25%,
or at least about 30%, or at least about 35%, or at least about 40%, or at
least about 45%,
or at least about 50%, or at least about 60% or even greater than a
compressive strength
of the cementitious composite in absence of graphene; or (b) a tensile
strength of at least
about 15%, or at least about 20%, or at least about 25%, or at least about
30%, or at least
about 35%, or at least about 40%, or at least about 45%, or at least about
50%, or at least
about 60% or even greater than a tensile strength of the cementitious
composite in the
absence of graphene; or (c) any percentage of (a) listed above and any
percentage of (b)
listed above. As used herein compressive strength is measured by a Forney VFD
(Variable Frequency Drive) automatic machine with dual load cells for maximum
accuracy. The tensile strength is measured by split tensile (Brazilian) test
to measure the
tensile strength of the cylinders. The specific jigs hold the cement or
concrete cylinders
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so that the uniaxial compressive force applied to the center lines of the
bottom and top
surface of the samples causes the tensile stress between the points of
contact.
[0041] The amount of graphene in the composite may
vary depending upon the type
and amount of cement, concrete, the type and amount of graphene, and the
desired
properties of the composite. Generally, the amount of graphene in the
composite is at
least about 0.005%, or at least about 0.01%, or at least about 0.03%, or at
least about
0.05%, or at least about 0.1%, or at least about 0.50%, or at least about 1%,
or at least
about 2%, up to about 3%, or up to about 10%, by weight of cement.
[0042] The process to make the composite may vary
depending upon the desired
characteristics of the composite, equipment available, and the materials to be
employed.
Generally, the process comprises mixing a reaction mixture comprising: (a)
cement, and
any other desired ingredients such as aggerates with (b) water which contained
grapheme
already homogenized in it, for example via shear mixing. Alternatively, the
solid
ingredients including cement and graphene can be dry mixed, for example using
ball mills,
and then mixed with water in some embodiments. The mixture is typically cured
by any
convenient curing mechanism. The curing conditions such as moisture,
temperature,
and time may vary depending upon the ingredients of the composite and desired
characteristics.
[0043] In some embodiments the dispersion of
sheared graphene may include a
surfactant in an amount to facilitate dispersion of the graphene in water.
Such
surfactants may vary depending upon the graphene and amount employed. However,
typical surfactants may be a poloxamer such as poloxamer 407 (Pluronic F-127)
or
commercial household surfactants such as dishwasher surfactants (Fairy Liquid,
Finish),
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If employed, the surfactant may be less than about 2%, or less than about
1.5%, or less
than about 1% by weight based on the total weight of the sheared graphene and
water
dispersion. In some embodiments, the surfactant can be used in shear
exfoliation of
graphene in water too.
[0044] In some embodiments, the surfactant is
Pluronic F127, sodium cholate,
Polystyrene sulfonic acid, Polyethylene imine, Sodium dodecyl sulfate, Sodium
dodecyl
benzene sulfate, Gum Arabic, Cetyltrimethylammonium bromide, Phosphate
surfactants,
Ammonium surfactants, Carboxylate surfactants, Amine surfactants, Phosphonate
surfactants or non-ionic surfactants (such as TWEEN 20, TWEEN 40, TWEEN 60,
TWEEN 80, TWEEN 85, Brij 93, Brij S100, Brij 58, Brij L4, Brij C10, Brij 020,
Brij
S100, Brij 520, IGEPAL CA-720, IGEPAL CO-520, IGEPAL CO-630, IGEPAL CO-
720, IGEPAL CO-890, MERPOL HCS, MERPOL SE, MERPOL, SH, MERPOL A,
Triton N-100, Triton X-100, Triton X-114, Triton X-405, Polyethylene glycol Mw
= 100
to 50,000 Wmol) or combination thereof
[0045] The water to cement ratio is generally at
least about 0.15, or at least about
0.17, or at least about 0.3, or at least about 0.4, oral least about 0.45, or
at least about 0.5,
or at least about 0.55, and up to about 0.7, or up to about 0.6, or up to
about 0.5, or any
ratios in between.
[0046] The graphene to water ratio is generally at
least about 0.05 get, or at least
about 0.10 g/L, or at least about 0.5g/L, or at least about 0.7g/L, or at
least about lg/L, or
at least about 2g/L up to about 10 g/L, or up to about 8 g/L, or up to about 6
g/L, or up to
about 5 g/L as well as all ratios in between.
[0047] The cement or concrete can have any typical
additives such as, for example,
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plasticizers, retarders, air entrainers, foaming agents, etc as desired.
Specific Embodiments and Examples
[0048] The present invention describes a novel technology utilizing the
fundamentals of
cutting-edge materials science, chemistry, advanced nano-engineering to create
cementitious composites reinforced by various forms of carbon-based
nanomaterials
including mono, few and multi-layer graphene and/or quantum dots. Our results
show
that that even small loadings of carbon-based nanomaterials significantly
enhance the
physical properties of the composites (where the matrix can be cement,
concrete,
polymers, etc).
[0049] In some embodiments, our invention includes treatment of various
graphene,
graphite, and their sources (for example coal), and their mixture in
cement/concrete,
creating a rich library of measured composite properties.
[0050] In one embodiment, graphene (for example, obtained from various sources
and
method) was dispersed in water/Pluronic (F-127) solution (for example, 1%) at
various
concentrations (for example, from 1 to 10 g/L). The dispersion was agitated
using shear
mixer (SiIverson L5MA) for 15 min at the speed of 5000 rpm. Next, the graphene
suspension in water was mixed with Portland cement (type II/I) with water to
cement ratio
of 0.40. Next, the slurry was casted in 2"x2"x2" PTFE cube molds (for
compressive
strength) and in 1"x 1.5" cylindered molds (for tensile strength). All cubes
and cylinders
were taken out of the molds after 24 hours and placed in water for curing. The
compressive and tensile mechanical strength were measured after 7 and 28 days.
For each
graphene:cement ratio, 3 samples were casted and tested.
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[0051] In one embodiment, the compression strength tests were performed using
a
Forney VFD (Variable Frequency Drive) automatic machine with dual load cells
for
maximum accuracy. The 7-day results indicate ¨35% increase compared to the
control
sample even with tiny fraction of 0.1% graphene by weight of cement (Figure
1).
[0052] Due to brittle nature of cement-based materials, their tensile strength
is usually
obtained by indirect test methods such as the modulus of rupture test or
splitting tensile
test. We used the splitting test to measure the tensile strength of the
cylinders. The
specific jigs hold the cylinders so that the uniaxial compressive force
applied to the center
lines of the bottom and top surface of the samples causes the tensile stress
between the
points of contact (Figure 1). The 7-day results indicate at least 20% increase
in tensile
strength compared to the control sample (free of graphene) with only 0.1%
graphene
[0053] Figure 2 shows the compressive strength of 2" cement cubes after 28
days. The
percentage increase in compressive strength (after 28 days) was 22.99% when
the
graphene amount was 0.035 w%. The percentage increase in compressive strength
(after
28 days) was 25% when the amount of graphene was 0.05 w%. Comparison of 7 day
and
28 day compressive strengths indicate that graphene loading lead to rapid
strength
development of cement-based materials as well.
[0054] The aforesaid large enhancement in the properties of graphene/cement
composites is because of our synthesis method, which results in large
dispensability of
graphene and their extensive exfoliation in water where the homogenously
distributed
sheet-like graphenes act as templates to promote congruent growth of cement
hydrate
products. While not wishing to be bound to any particular theory it is
believed that perhaps
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covalent C-0 bonds/networks between graphene and cement hydrate products can
change
the hybridization of graphene from sp2 to sp3 upon covalent bond formation,
greatly
enhancing the properties of the composite. This change, along with electron
release in the
vicinity of their interfacial region, can lead to homogenous, inter-mixed and
intercalated
composites with improved properties.
[0055] The graphene used in this work can be mono and/or few layer graphene
(<1ess
than 10 layers), the layer stacking can be organized or disorganized or mixed,
the layer
stacking can be bernal (AB) stacking, randomly oriented stacking
(turbostratic), or the
combination thereof Graphene used in this work can also be of different
lateral
dimensions, be nanoplatelets, or polyehedra, disoriented, misoliented,
twisted, or any
combination thereof Turbostratic graphene has little to no order compared to
conventional AB (bemal) stacking and may be easier to disperse in a solution.
[0056] The graphene in the above examples was turbostratic with mono and/or
few
layers, and obtained from carbon black, rubber tires, plastic waste derived
pyrolysis ash,
etc, as the raw material. However, the raw materials for the graphene used can
be any
source of carbon. The carbon feedstock can change the composite properties
because
the feedstock may play a role in the size and shape of the produced graphenes,
and its
quality (i.e. presence of defects) and thereby the composite properties.
[0057] The source of carbon can include but is not limited to any single or
combination
of the following: graphite, feces, plastics, vinyl polymers, condensation
polymers, step-
growth polymers, chain-growth polymers, living polymers, rubbers, titanic
acid,
carbohydrates, rice powder, food waste, food, coal, organic waste, organic
material,
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bituminous coal, coke, shungite, asphaltenes, acetylene black, carbon black,
petroleum
coke, oil, petroleum products, carbon from the stripping of the non-carbon
atoms off of
natural gas or oil or carbon dioxide, wood, cellulose, leaves, branches,
grass, biomass,
animal carcasses, fish carcasses, proteins, and mixtures thereof The type of
coal is not
particularly limited and includes, for example, a coal selected from
anthracite, bituminous,
sub-bituminous, lignite, or a mixture thereof Similarly, the type of plastic
is not limited
and includes, for example, a plastic selected from high-density polyethylene
(HDPE),
low-density polyethylene (LDPE), polyvinyl chloride (PVC), polypropylene (PP),
polyacrylonitrile (PAN), Polyethylene terephthalate (PET), or a mixture
thereof
[0058] In another embodiment, we tested graphene made from HDPE, or PP or
mixture
of the two. Similar to the previously mentioned synthesis method, cement
composites
from HDPE and PP mixture were tested_ It was found that addition of at least
0.035%
of HDPE-derived graphene can increase the compressive strength of Portland
cement by
30% (Figure 3). Here, the graphene may be sheared in water at a concentration
of 0.5,
or 0.7, or 1.0 or 1.5 g/L with a suitable amount of a suitable surfactant. In
that vein,
0.025, or 0.05, or 0.1, or 0.2 or more wt% of sodium cholate or a Pluronic
may be useful
as a surfactant.
[0059] In another embodiment, we created 2" cement cubes reinforced with
turbostratic
graphene made from a mixture of each of carbon black:acrylonitrile Butadine
Styrene
(5%:95% weight ratio), hereto called CB:ABS, or carbon black: gelatin (5%:95%
weight
ratio), hereto called CB: Gelatin, or carbon black: humic acid (5%:95% weight
ratio),
hereto called CB: gelatin. Here, the graphene may be sheared in water at a
suitable
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concentration of surfactant, e.g., from 0.1 to about 1.5 g/L, e.g., 0.7 g/L
with sodium
cholate or Pluronic F-127 as a surfactant. The 7-day compressive strength
results are
shown in Figure 4. The cement samples with CB: HA fillers show >27% increase
in
compressive strength.
[0060] In another embodiment, we created concrete samples. First, turbosratic
graphene
may be shear mixed for a suitable time at a suitable temperature (10, or 15,
or 20, or 25
min at the speed of 3000, or 4000, or 5000 rpm) in water at e.g., from 0.1 to
about 1.5
g/L, e.g., 0.7 g/L with 0.025, or 0,05, or 0.075 wt% of a Pluronic or sodium
cholate as
a surfactant. Next, the graphene suspension in water was mixed with Portland
cement
(type II/I) with water to cement ratio of 0.57, to which we added sand and
gravel at the
following ratio, cement : sand : gravel 1:2:3. Next, the mixture was casted in
4"x8" molds.
All cylinders were taken out of the molds after 24 hours and placed in water
for curing
The compressive and tensile mechanical strength were measured after 7 and 28
days.
For each graphene:cement ratio, 3 samples were casted and tested. Figure 5
shows
representative results, demonstrating >41% increase with respect to the
control concrete
sample free of graphene. By repeating the above procedure using commercial
graphene
nanoplatelets (in lieu of turbostratic graphene), we obtained >73% increase in
compressive strength after 28 days.
[0061] In some embodiment, small amounts of three types of tw-bostratic
graphene
obtained from carbon black derived from pyrolyzed rubber tires (hereto called
graphene
I), from waste plastics derived pyrolysis ash (hereto called graphene II) and
shredded raw
rubber tires (hereto called graphene III) were sheared mixed (as described
earlier) in water.
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Next, each solution was added to ordinary Portland cement (OPC), flyash C, and
Slag and
each cured for 7 days to yield 1" cube composite pastes (Figure 6 to 8). In
other
experiments, we included sand and gravel to these paste mixtures to create
4x8" concrete
cylinders (Figure 9 to 11). Significant increases in compressive strength were
observed
in all cases, with strength increasing as content of turbostratic graphene
increases,
reaching an optimal loading between 0.05 to 02%. For example, the compressive
strength
enhancement of at least 15 % was measured for 0.1% enhanced OPC paste, and a
15%
increase was observed for OPC concrete. The data for concrete are only shown
for an
optimal wt% of the specific graphene in the specific cement.
[0062] In some embodiments, the feedstock of graphene II (or generally carbon
feedstocks that have low electrical conductivituy) had between 0 to 10%
conductive
materials such as commercial carbon black, metals, or graphene.
[0063] In some embodiments, the average sheet size of graphene 1,11,111 was
around 20
0-300 nm containing around 10-15 sheets stacked.
[0064] In some embodiment, the shrinkage of the above composite pastes and
concrete
reinforced with graphene I, II, and III were at least 10% lower compared to
the samples
without!, II, and III as measured by average changes in the cross-sections of
the samples.
[0065] The graphene used in the above example can be manufactured with various
methods including but not limited to various top-down approaches such as
direct
sonication of graphite, chemical exfoliation of graphite, micromechanical
exfoliation,
electrochemical exfoliation, super acid dissolution of graphite,
electrographitization, etc,
and various bottom-up approaches such as chemical vapor deposition (CVD),
epitaxial
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growth, arch discharge, joule heating, flash joule heating, pyrolysis,
unzipping of carbon
nanotubes, confined self-assembly, reduction of CO, one-step or multiplestep
non-
dispersion methods of producing graphene, etc.
[0066] This invention can be applied to less than or more than 10 layers of
graphene.
Graphene with more than 10 layers is often times called graphite, thus the
invention can
also be applied to chemically expanded graphite or thermally expanded graphite
(TEG),
non-planar graphite, etc.
[0067] In one embodiment, we created cement and concrete samples reinforced by
thermally expanded graphite (TEG). First, TEG was shear mixed (15 min at the
speed
of 5000 rpm) in water using sodium cholate as a surfactant. Next, the TEG
suspension
in water was mixed with Portland cement (type II/I) with water to cement ratio
of 0.4.
Next, the mixtures were casted in 2" molds. For creating concrete samples, we
added
sand and gravel to the cement slurry at the following ratio, cement: sand:
gravel 1:2:3.
MI cement cubes and concrete cylinders were taken out of the molds after 24
hours and
placed in water for curing. The mechanical strength were measured after 7 and
28 days.
Figure 12 shows representative 28 day results, demonstrating >20% increase in
compressive strength of concrete samples with respect to the control concrete
sample.
[0068] The present invention can be used with or without surfactants. In one
embodiment, graphene (obtained from various sources) was dispersed in only
water at
various concentrations, for example, from 1 to 10 g/L. In another embodiment,
the
amount of surfactants can be decreased or increased to tune the composite
properties. In
another embodiment, the surfactant can be household detergents such as Fairy
washing-
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up liquid (commonly known as Fairy Liquid, FL), a common household dishwashing
liquid, with a composition of 15-30% anionic surfactants, 5-15% nonionic
surfactants.
[0069] In some embodiments, we bypassed the use of graphene manufactured by
top-
down or bottom-up approaches such as those derived from arch discharge,
exfoliation
from graphite, joule heating, flash joule healing, etc. Instead, we turned
various carbon
feedstocks (for example, coal) "directly" to carbon-based nanomaterials with
quantum-
dot and/or graphene/graphitic structures. This direct conversion of carbon
feedstock to
carbon-based nanomaterials for cementitious materials in shown in Figure 13.
[0070] In some embodiments, we focused on coal as a source of carbon and in
some
embodiments we oxidized the coal using a suitable oxidizing agent such as
nitric acid,
sulfuric acid, or potassium permanganate followed by homogenization in water
using a
suitable mixer such as a Banbury mixer, a shear mixer, a Haake mixer, a
Brabender mixer,
a sonicator, or a rotor-stator, jet mill or a Gaulin homogenizer.
[0071] In some embodiments, the oxidizing agent can be from KMn04, HNO3,
KCI03,
H2SO4, HC1, H3PO4, KNO3, NaNO3, or chromates (such as (NH4)2Cr207, Cr03,
Bis(tetrabutylammonium) dichromate, IC2Cr207, Pyridinium chlorochromate,
(C5H5N
)2.H2Cr207, Na2Cr207, Na2Cr207.2H20, peroxides (H202, Ca02, C14H1004, C
8H1806, C4H1002, C9H1202, C18H2202, CH4N20.H202, Li202, C 10H1406, C
8th 802, C24H4604, Ni02, Ni02.xH20, Na202, Sr02, Zn02) or Peroxy acids an
d salts (such as Cl1H21BF4N202, C7H5C103, C16H10Mg010.6H20, C2H403) or
sulfur-based oxidizing agents (such as (NH4)2S208, HKO5SØ5HKO4SØ51C204S,
K2N07S2, 1C208S2, Na208S2, C3H7NO4S, C5H5NO3S, C6H15NO3S, C3H9NO3
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S. C12H27N035) or hypervalent iodines (C13H8Br2F3103S, C16H23104, C13H8F
51035, C15H14F31035, C1OH1OBF4IN2, C1OH1OBF4IN2, C10F1H04, C16H15Br
F31035, C13H13108, C13H13108, C12H10C11, C13H131045, C7H5104, C8H5106,
C8H5I06, C16H15F3IN05S, H5106, C14H9F61035, C7H61K03S, 11(04, INa04,
1121Na306, C811201N04) or Hypochlorites (Ca(0c1)2, Na0C1) or osmium-based oxi
dizing agents (0s04, K20s04.2H20, Perchlorates, Al(C104).3.9H20, Ba(C104)2, C
d(C104)2.4H20, Cd(C104)2.xH20, CsC104, Cu(C104)2.6H20, Cl7H26N302S - CI
04, C131n012 - xH20, C13Fe012 - xH20, C1208Pb - xH20, C1208Pb - 3H20, Li
C104, LiC104.3H20, MgC104, Mn(C104)2.xH20, Hg(C104)2.xH20, Ni(C104)2.6H
20, HC104, DC104, KC104, Sc(C104)3, AgC104.3H20, AgC104.1H20, AgC104.x
H20, NaC104, NaC104.H20, C116H36C1N04, Zn(C104)2.6H20) or other oxidizing
agents such as H8CeN8018, H12Mo12N3040P.xH20, C9H14NO, C36H30CrO4Si2
CIOH15NS, C7H7CINNa02S.3H20, C7H7CINNa02S.xH20, C6C1402, C6H5C1
NNa02S.x1120, C8C12N202, C4115C103, C11H1INO, C8HC14NO3, C81112NO2,
MgMn208.x1120, C3H3C103, C5H11NO2, BF4NO, C2Br202, C2C1202, H2Mol2
040PAH20, K04Ru, 02Se, C2C12N3Na03, C3C12N3Na03.2H20, MnNa04.H20,
MnNa04, CNa203 1.5H20, Mo12Na3040PAH20, C9H18NO, C6N4, C21H28NO
4Ru, C3H9NO3S, C3H9N0.2H20, or the combination thereof
[0072] In some embodiments, our invention allows up to full control over
various ranks
of coal, and the homogeneity and water solubility of the carbon product.
[0073] In some embodiments, first, a desired amount of coal feedstock is added
into
water with a suitable amount of oxidizing agent. Oxidizing agents include, for
example,
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acids such as nitric acid, sulfuric acid, and mixtures of sodium or potassium
permanganates with, for example, peroxides like hydrogen peroxide. For
example, a
suitable volume percent of potassium permanganate, e.g., less than 10v% such
as 5v% or
6v%, or 7v%, or 8v% of Potassium permanganate can be mixed with hydrogen
peroxide
in a suitable ratio, e.g., (2:1 or 1:2 or 1:1 ). After stirring for a desired
time (e.g. 1 h, 2 h,
3h) at a desired temperature (25 C, 50 C, 100 C, 150 ct, 200 `IC) the solution
was
decanted and centrifuged to get all the solids. Second, the solid product was
suspended
in water at a concentration of ¨0.2-2g/L (depending on the coal feedstock),
followed by
high shear mixing for 10 min at 10000 rpm. This water solution that contains
carbon-
based materials was supplied with optimal ratios to cement to make
cetnentitious binders
or, to a mixture of cement, sand, and gravel to make concrete. Alternatively,
this solution
was supplied as an additive with optimal ratios to a mixture of cement and
water to make
cementitious binders or, a mixture of cement, water, sand, and gravel to make
concrete.
The whole mixture can be mixed on job sites using conventional cement and
concrete
mixers or the like.
[0074] In some embodiments, Potassium permanganate (K_Mnat) and hydrogen
peroxide (1-1202) can be mixed in a suitable ratio, e.g., 2:1 or 1.5:1 or 1:2
or 1:1.5 or 1:1.
The stock solution is transferred into 50 L of water with a suitable
concentration, for
example, lv%, or 3v%, or 5v%, or 7v%, or 10v% of KIVIn04/H202. Next, a desired
amount of feedstock (-1 kg of coke) was added into the 50 L of oxidant
solution. The
solution was stirred for a desired time (e.g. 1 h, 2 h, 3h) at a desired
temperature (25 C,
50t, 100 C, 150 C, 200 *C). Then, the solution was filtered using centrifuge
to get
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the solid carbon product. Next, this solid product was suspended in 5L water
at a
concentration between ¨0.2 to g/L, followed by
shear mixing for 10 min at a speed
of 10000 rpm. Generally the suspension has a range of carbon-based
nanomaterials such
as quantum dots and/or graphene/graphitic-like sheets with different
thicknesses, lateral
sizes and defects. The suspension was used to cast 2" cement cubes with water
to
cement ratio (w/c) of 057 (or lower) using Portland cement types IL To create
concrete
samples, we added sand and gravel to the cement mixture with cement: sand:
gravel ratio
of 1:2:3 (with w/c=0.57) and casted 4"x8" concrete cylinders. After 24 his,
the samples
were removed out of the mold and immersed in water for curing up to 7 and 28
days. As
a reference, graphite as a layered feedstock may be employed with or without
chemical
treatment. In some cases a Sodium cholate surfactant may be employed to make
it more
dispersible in water, followed by similar shear blending. We also can use
industrial
grade graphene nanoplatelets as feedstock and shear blend it in water.
[0075] Figure 14a-b show the compressive strength of 2"cement cubes reinforced
by
mainly bituminous coal, b-coal, (Figure 14a) and calcined coke (Figure 14b) at
7 days.
Figure 14c-d show the compressive strength of 4"x8" concrete cylinders at 7
day (Figure
14c) and 28 days (Figure 14d). In Figure 14d, the data is shown for the
optimum wt% of
carbon in cement. Interestingly, graphene represents the most increase in
strength of
concrete in both 7 and 28 days, reaching 141% and 81% with only ¨0.035 wt% of
weight
of cement (tiny fraction). Second to graphene, coke functionalized via
K.Mna4/H202,
demonstrated 62% and 42% increase in strength at 7 days and 28 days,
respectively with
only 0.05 wt% of coke in cement (again a very tiny fraction). In both cases,
the 28 day
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strength is lower than 7 day strength, suggesting more contribution of such
carbon-based
nanomaterials to early strength development. However, the increase in strength
after 28
days is still quite encouraging given the very low wt% of the fillers. To our
knowledge,
there is no any other report for such increase in strength with these low wt%
of coal-
derived carbon nanomaterials directly used in cement composites.
[0076] Remarkably, other coal-derived carbon materials (bituminous coal,
graphite) also
contribute significantly (>35%) to the mechanical properties with similarly
low wt %.
This will have important implication on best utilization of coals at different
geographies.
Note that addition of raw coals (bituminous, coke, etc), even if shear blended
at high rpm
or grinded, did not help and in many instances chemical treatment is needed.
Similarly,
the chemical treatment alone in many cases does not yield good results and its
combination with the shear blending is necessary. Our synthesis method, along
with
various wt% of carbon-based nanomaterials (for example quantum dots,
graphene/graphitic structures, etc) will also lead to increases in other
composite properties
such as lower shrinkage, enhanced tensile strength, modified viscosity, higher
thermal
and electrical properties and durability of cementitious materials. Such
property
enhancement at these low weight fractions of carbon-based nanomaterials and
using
inexpensive feedstocks is unprecedented.
[0077] In some embodiments, we used various treatments such as oxidization
(with
sulphuric acid, ICMn04), further oxidization, ball-milling, etc, and various
feedstocks
such as charcoal, biochar, biochem, etc as shown in Figure 14.
[0078] In some embodiments, the weight percentage of the carbon-based
nanomaterials
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in the cement may be much larger and the various properties may be optimized
further.
[0079] The foregoing description details certain
preferred embodiments of the
present invention and describes the best mode contemplated. It will be
appreciated,
however, that changes may be made in the details of construction and the
configuration
of components without departing from the spirit and scope of the disclosure.
Therefore,
the description provided herein is to be considered exemplary, rather than
limiting, and
the true scope of the invention is that defined by the following claims and
the full range
of equivalency to which each element thereof is entitled.
[0080] The present invention has applications in
several areas including (but not
limited to) general cement and concrete industry, roads, building, pedestrian
ways, glass
fiber reinforced concrete, application for extreme conditions including but
not limited to
well cementing for oil and gas extraction or geothermal wells, cement used in
nuclear
industry, cement used in army and military applications as well as for airport
infrastructures and runways, and other applications of cementitious
composites.
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